-- Power Up
an ATX PSU without a Motherboard
-- 7.18.2001
-- By:GideonX-- Page: 1

Today we have a quickie guide on powering up a power
supply without the aid of a motherboard. This guide is aimed
at the user who needs just a little more power to get that peltier
working or to get more fans in your box. A 250W may not be
enough for those chores, so here we have a solution. Get
another PSU just to power those specific components.

As most of you know, motherboards usually come with
just one ATX plug. How that works is, the two pins on the row
of your motherboard is usually connected by a momentary switch.
To put it in layman's terms, the switch you press in front of your
case causes a 'jump' in those two pins which in turn tells the power
supply to turn on.

The above picture is the general design
of an ATX plug. The green box and black box are the exact
locations on the plug we will be working on. The green (Pin
14) is designated as the power on line, while the black (Pin 13) is
just a ground line.

To keep a PSU alive, a momentary switch is not
needed since you will not be going through a motherboard. A
permanent switch is needed though, to keep it powered as long as
needed. To do this, we will need the follow:

SPDT (single pull, double throw) Switch

ATX Compliant Power Supply

That's it, all we need is a switch that can stay on
all the time and the PSU will be continuously powered. Some
people have mentioned that just taking a wire and connecting the two
points on the plug will do it. To turn off the unit, just hit
the switch on the back of the PSU. Well, what happens if you
don't have a switch on your PSU? That's where the SPDT switch
comes in handy.

Here are the two wires that come out
from the SPDT switch, you don't really have to worry about which
goes where since the switch will just act as a pass through.
Either wire can be placed within the green or black connector on the
ATX plug.

You can solder those points into those
plugs for a more permanent solution. We just placed it in
position for the time being to make sure everything was working.

To test if the little mod worked, we
will attach a small heatsink with a molex connected fan to the power
supply. We turned the power supply switch to the on position
after attaching our SPDT switch. The SPDT switch will be used
to power on/off the unit from now on. It is fortunate we have
both switches to utilize, but if you are stuck without a master
on/off switch on your PSU, the SPDT can be used instead.

And there you have it, we have our
little heatsink spinning up just fine. Make sure when you plug
more devices onto your extra PSU, to power down first to prevent any
sparks and failures. Take it from us : ) Good luck!